System and method of



March 13, 1934. J. H, HAMMOND, JR R 19,107

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J. H. HAMMOND, JR Re. 19,107 SYSTEM AND METHOD OF COMMUNICATION ori inai Fil ed Sept. 2. 1926 a Sheets-Sheet 2 Ill]:

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ATTORNEY March 1934} J. H. HAMMOND, JR Re. 19,107

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SYSTBI mm ls'mqn or c'ouuuxcmr'ou 8 Sheets-Sheet 8 Original Filed Sept. 2. 1926 M m S w v 68$ anvcnto'c JOHN PHYS HAMMOND JR. 351 I113 fluouwq w w S MM QQQSQ QNQ new; Mar. 13, 1934 other directional aerials which have been rather UNITED STATES PATENT-OFFICE Y ere-rm AND METHOD or oorrmmrcarron John Hays Hammond, Jr., Gloueeatefillhsa ,Original No. 1,785,307, dated December 16, 1930, Serial No. 133,094, September 2, 1928. Application for reissue October 24, 1931, Serial No.

Some of the objects of this invention are to provide an improved means and method for determining the bearings of-a ship at sea, thelocation of a ship at'sea with respect to known points on the shore, the relative velocity of a ship toward or from known points on the shore, and speed of a ship. Still other objects will hereafter appear as the description proceeds.

In the accompanying drawings, Fig.1 shows a general lay-out of a systememlmdy theim vention.

Fig. 2 is a diagrammatic representation of the radio transmitting installation.

Fig. 3 is a diagrammatic view'of the receiving apparatus.

Fig. 4 shows the electrical connections of the radio receiver... t

Fig. 5 is a view of the graphic1recorden- Figs. 6 and '7 are views of the bearing indicator. 1

Fig. 8 is a diagrammatic drawing of the connections for the sound transmitter, and Sonic Depth Indicator. i

Fig. 9' is a die-era beat installation.

Fig. 10 is a sketch showing the method of plotting a vessels position.

Heretofore the general method of indicating a erratic in operation and expensive to-construct and operate, and the present-invention aims to provide a radically differentand more dependable system and, method described below."

Purposes-0f this invention are to enable the navigator of a vessel approaching the shore to ascertain his location with reference to fixed points along the shore line and also his velocity in respect to one or 'allof these points. The sys'tem'for obtaining such-information comprises a source of sound,.such as an under-water oscilator, aboard the vessel, micro-' phones located at. known points along the shore' lineconnected by submarine cables'to a central radio transmitting station, a radio receiver on board the vessel and preferably agraphic recorder attached to said receiver.

From the radio transmitting station, signals modulated by they sound waves picked-up by the microphones are received on board the vessel and from these received waves the ship's position, ve-

locity and other data relative to its movement may be ascertained and computed.

in Fig. 1 a typical installation is shown in which micrcphones numbered 1, 2 and 3 are attached Claims. (Cl. T -352) The vessel 4 carrlesa source of a zero 'or B frequencies, which can located on the shore. of sound to produce sound waves in the water as indicated by 8.

To get an indication of the speed at which the ship approaches a fixed point, such as station 1. the ship's sound oscillatoris energized to send out a sound wave, for example, of 5,000 cycles. The

by cables to radio station'5 frequency of the sound received at microphone station 1 will be determined by the frequency of the sound wave emitted from the oscillator and the velocity of the vesselcarrying the oscillator relative to the microphone. This is according to the Doppler principle. As an illustration of this principle, take, forexample, a vessel emitting a note of 5,000 cycles going directly toward the receiving station at a speed of 30 knots (15 meters;

per second).

y This is obtained by applying the formula I I n n vi'l'vz where nn=observed frequency ns=sending frequency salt water V1=velocity of sound in (1503 /sec) Vz=velocity of the ship relative to the microphone from which it can be seen that the velocity of ship can readily be calculated.

The system in its simplest form may best be describedby reference to Fig. 1. The antenna 21 of the coastal radio transmitting station 5 is en'- 'ergized by a radio frequency generator 22 connected to a, modulating power amplifier 20 working, for example, at 300 k. c. (1000 meters) This power amplifier of the carrier wave or current of A frequency, is modulated by three intermediate be 10,000 cycles, 20,000 cycles and 30,000 cycles, or any other values desired forthe p Each of these different intermediate frequencies of whichthere maybe any convenient desired number are in turn, modulated by the sound waves, which may have been amplified if found necessary or desirable, coming from the microphones 1, 2 and 3, respectively. These microphones are suitably placed so as not to be disturbed by undesirable sound reflections from the shore. Any'desired number of microphone stations may be used.

"1A transmitter of the proper design is shown schematically in Fig. 1 where as shown the microdevices 1 4, 15 and 16 in which the microphone The observed frequencyat the sta- 1 tion will then be 5050 cycles.

phones at 1,2 and 3 are connected to modulating i currents respectively modulate the B frequency currents from generators 17, 18 and 19 which act together to cause a multiple modulated carrier wave to be impressed on the antenna 21 by the power amplifier 20. Such a radio'transmitter may emit a carrier wave of 300 k. c. for example, upon which have been super-imposed intermediate waveshaving frequencies of 10,000 cycles, 20,000 cycles and 30,000 cycles respectively, the amplitude of each of these intermediate waves being controlled or modulated by the sound waves picked up by their associated microphones connectedthrough the modulators 14,15 and 16 respectively and also through sound amplifiers if so desired (not shown).

The electrical connections for the transmitter as shown in Fig. 2 are substantially equivalent to the well known complex wave transmission system. The antenna 21 is connected to the ground at 67 and coupled to the power amplifier 64',

through coils 65 and 66. The amplifier 64 amplihes the carrier wave produced by the alternator 63 which delivers energy through the coupling.

6162. The amplified energy is modulated by the B frequencies produced by tubes 33, 34 and coupled through coils55, 45, 42, 56, 46, 43; and 57, 4'7 and 44 respectively. Tuning condensers 48, 49 and are inserted in the circuit as are also by-pass condensers 60, 58 and 59 in the usual manner. The customary biasingbattery 54 and grid leaks 51,52 and 53 are inserted in their proper relation in the circuits. The B frequency currents are modulated by the.C frequency current transmitted from the microphones 1, 2 and- 3 through transformers 21, 22 and 23 and battery 24 to the modulating tubes 25, 26 and 27. These modulating tubes also have the usual C battery as indicated at 28. Plate current is supplied through the generator 29 through choke coils 30, 31 and 32; stoppage condensers 36, 37 and 38 are placed in the usual'positicn in the plate filament circuits to open the circuits to direct currents. e

To determine the relative position of a ship with respect to known points on land, the complex modulated carrier wave radiated by the above described transmitter is received on board picked up by the respective microphones at the transmitter. Connected to each of the, 0. aequency detectors is a volume indicator which produces a graphical record of the relative intensity I of the sounds striking microphones 1, 2 and 3. The intensities thus recorded are substantially inversely proportional to the distance from the sound source to each of the microphones.

Therefore, such a record indicates'the distance from the ship to the various microphones, or, in

other words, flxes'the position of the ship with reference to the lmown points at which the microphones are located. A further description of a recordersuitable for use as above mentioned appears below. The output from the C. frequency detectors may be fed to D frequency detectors for p p ses later tolbe described.

The apparatus indicated in P18. 3

- and 157.

and as shown in-more detail in Fig. 4 embodies the usual double detector system for receiving complex modulated waves. The modulated wave is received in the usual manner by the antenna connected to a single circuit tuner 101, 102 supplying detector 106 equipped with the ordinary grid leak and condenser 104 and 105. This is an A frequency detector. The plate circuit of this detector feeds three resonant circuits tuned respectively by condensers 110, 111, 112, to the three 13 frequencies.

ThreeB-frequency detectors 122, 123 and 124 are provided each with the usual grid leak and condenserand tuned input circuit. These demodulating devices take their input power from the above-mentioned tuned filter circuits and deliver-their outputs to the 0" frequency detectors 143, 144 and 145 the frequency super-imposed on each B frequency channel, that is, of course, the

C-frequency. The input circuit of each of these" three C detectors comprises the usual tuned circuit. Each detector is provided with a grid bias battery of sufilcient voltage to bring the detecflowing through it and this current is in turn dependent upon the strength of the signal input, it will be seen that the graphical record will show the amplitude of the received 0 frequency.

For the purpose of indicating the velocity of the ship relative to the microphone stations, the output from each of the C frequency detectors is taken to a D frequency detector which is connected to a local oscillator having, in this case, a frequency of 5050. cycles. Beat frequencies result from the heterodyne action between each incoming C frequency and current from this local oscillator. The resultant beat note will be 50 cycles when the ship is neither approaching nor departing from the microphone; At a speedof 30 knots a zero beat frequency would indicate a speed of 30 knots toward the microphone and a beat of 100 cycles would indicate a speed of 30 knots away from the microphone; this will be described in more detail later. The exact frequency of the beat note in each of the three channels is recorded by means of an attached frequency, n cator." Continuing with the description'of the receiver, as shown in Fig. 4 we come to the D-frequency detectors 155, 156 The input circuits of these are of the usual form. 7

Since heterodyne reception isdesired, an oscillator 158 is provided. This oscillator may be utilized to furnish the heterodyning frequency to all D-'detectors. The input to these three I D-detectors is taken from the three corresponding C-frequency outputs. The resulting heterodyned frequencies which will' vary between the limits of 0 and-100' cycles. are led to the-associated frequencyjndicatofs 1'10, 171 and 172.

, Indicators shown at 170, 171 and 172 are for the purpose of indicaflng frequencies between 0 and 100 cycles andcan be'of anviwel'lr known ype, preferably of a moving Minten'atypex flm.

times called the resonant circuit frequency indicator. The pointers of these frequency indicators carry 1d pencilv so that they graphically record their readings on a moving strip of paper.

The two frequency indicators 173' and 174 which are used in the simple bearing indicator" are instruments similar to the frequency meters 1'10, 171 and 172 except these are equipped with pointers moving in a suitable mannerover a scale. The moving coil system in such a meter controls a pointer which moves in response to any change in frequency. In this invention the pointer may be equipped with a. markerso that graphical record frequency changes are obtained from which the velocity of the ship relative to the microphone stations can readily be calculated or computed.

The switches 178 and 190 allow the telephone receivers or indicator 179 to be switched into either the C-freque'ncy detector or D-frequency detector circuits for'the purpose of checking, by

ear, the operation of the system and allowing the operator to make desired observations.

In order" that the navigator oi the ship-may have a continuous graphic record of his proximity-and velocity of approach to the fixed station, a graphic recorder may be used as illustrated in Fig. 5. The strip of paper 219-219 upon which the record is made is drawn through the recording device by a synchronous motor 203 driven from a generator attached to the ships propeller shaft. Marking on this paper; which is ruled with suitable lines 217, 218 are a set of six markers or pens, 211, 212, 213, 214, 215, 216 in two groups or three each. The markers of the'first are moved across the papers by means of a micro-ammeter movement which, being connected to theoutput of the C frequency detec-' tors, serves in a well known manner to indicate the intensity of the sounds striking microphones 1, 2 and 3 to which they are respectively connected by the radio link. If no sound strikes these microphones the output of each 0 frequency 1 detector will be zero and the pens will trace a' mark along the zero line printed on the paper strip. -A sound originating near microphone 1 would cause the marker of the intensity indicator connected to detector C1 to move across-the paper and indicate considerable intensity, while the pen connected to C2 energized by microphone 2 will show less intensity and the pen connected to C3 energized ,by microphone 3 will show still less intensity.

The other group of three indicators indicate the ships velocity with reference "to the microphone stations 1, 2 and 3.. These indicators comprising frequency meter movements are connected to the D frequency detectors D1, D2 and D3 in such a manner that they will trace upon a paper record, lines showing the variation in frequency of the sound waves striking the individual microphones to which they are linked by radio thereby indicating indirectly the ships velocity in reference circu t of the three C irequency detectors in the time whether this speed is toward or away from the station microphone to which each frequency indicator is connected. The operation of this system is as follows:-

A vessel steaming at say 30 knots per hour 1 quency generator.

ound marine oscillatonsends out an under-water sound wave of 5,000 cycles. -,We will assume that the J position of the ship is abreast of microphone station 2 (Fig. 1) and that the, ship is moving in a direction indicated by. the arrow. There will then be received at microphone station 1, a frequency of say 5,030 cycles, the increase of 30- cycles being due to the component oi the velocity of the vessel toward microphone station 1. The sound waves received by microphone 2 will be 5,000 cycles, there being approximately no 'velocity component in this direction and that received by microphone station 3 will be 4,970 cycles inasmuch as the vessel is noving away from this I point. There will flow, therefore, in each of the three cables connecting the microphones to the radio station, currents of slightly different fre? quency, each of these, amplifiedif desired, will be caused to modulate its intermediate fre- We will assume the. microphone 1 is associated with the intermediate frequency of 10,000 cycles, microphone 2 with 20,000 cycles and microphone 3 with 30,000 cycles. These intermediate frequencies, having been varied in amplitude by sounds picked up by their associated microphones, are super-imposed uponthe carrier'wave and the resulting modulated complex carrier wave radiated into space.

This wave being received by the moving vessel, is successively detected in 'the usual manner "of detecting such' complex waves, resulting in obtaining in the output circuit of the C frequency detectors, the sound waves picked up by their respective microphones.

In the output circuit of detector C1, there will be flowing a current, whose frequency is 5030. cycles, in C2, 5000 cycles and in C3, 4970 cycles. The amplitude of each of these currents will be proportional to the strength of thesound wave which energizes the microphone of that particular channel, thus the amplitude of the signal coming from microphones 1 and 3 will be approximately equal and less than that received from microphone 2 due to the position of the ship which we have assumed to be as shown in Fig. 1. The relative amplitudes can be seen by inspecting the chart traced by the graphical recorder which is being run at a speed proportional to that of the ships propeller. From this record, the navigator can estimate the position of the ship with respect to the fixed microphone stations, as from the usual data taken from ships he knows the mileage traveled relatively to the water and the revolutions and slip of the propeller.

To obtain the velocity with'whichthe ship is moving with reference to these three points, a navigator would observe the companion record made by the three frequency indicating devices, these being operated indirectly from the output following manner:-

Referring again to Fig. 4-, the frequency derived 1 10 from 01 being 5030 cycles is actuated upon by a local oscillator generating 5050 cycles so that after passing through detector D1, the beat frequency would be 20 cycles. A voltage of this frequency when supplied to the recording mecha- 1 nism will cause a marker to move to a position corresponding to 20 cycles. The frequency reaching detector Dzis 5000 cycles hence the resulting beat note of 50- cycles would be indiiated in a similar manner upon the record as heterodyning the 4970 cycle output of detector C3. By suitable calibration the velocity of theship toward or away from any of the three fixed points may be read in knots per hour from the velocity traced by the graphic recorder. For instance, the position of the frequency marker should be along the middle or zero line for 50 cycles. For higher frequencies it should indicate on the side of this mid-line marked stern and for frequency lower than 50 cycles, the pointer should record on the side marked "ahead.

The principle involved in this invention can alsobe adapted to determine the distance between a ship and a fixed point. The system upon which this determination .can be made is as follows:

If a-sound signal is sent from the ship and received by a microphone located at a known point and this received sound signal is re-transmitted over a radio channel back to the ship, the time lapsed will give the distance from the ship to thefixed point since the velocity of sound in water and of radio waves in ether is accurately known. Using the apparatus previously described if the navigator desired to determine distance he would send a dot on "the ships under-water oscillator and listen for the return of this sound via radio by means of a sonic depth indicator, a device commonly used for measuring the lapsed time of echoes from the sea bottom. Such an arrangement is shown in Fig. 8. Means for doing this in accordance with the present invention are shown in Fig. 9 which will be described more in detail hereinafter.

In Figs. 6 and 7 are shown an embodiment of i this invention, the purpose of which is to enable the navigating officer of a vessel equipped with the apparatus described above to read from an (indicator the approximate bearings with respect 'to any fixed microphone station. Such a system comprises a sound source, sound waves in, water, a microphone located at a known point, a radio station emitting a radio wave preferably modulated bya complex wave, the sound waves picked up by the microphone, a radio receiver on board ship making possible the reception of the sounds picked up by the microphone, a recording device to accurately reproduce small differences in the frequency of said sounds as described above, and an indicator operated by said recording device. The operation'of such' a system would be as follows:

Assume that vessel 4 in Fig. 1 is speeding at a rate of 30 knots directly away from microphone station 1. The oscillator sends out a 5000 cycles underwater signal .from the ship's modulator.- This signal is received by microphone 1 as 4950 cycles due to the velocity of the vessel directly away from the fixed point. This difference in frequency is in accordance with the Doppler principle, previously mentioned. The 4950 cycle note picked up by the microphone modulates the 10,000 cycle B frequency which, in turn, acts on the carrier wave. I This carrier wave sent out from the coastal radio station, is picked up by the .radioreceiver on board the vessel where it is detected in the usual manner. The sounds picked up by microphone 1 will therefore be audible in the output circuit of detector C1 in theinanner explained above. The frequency of this circuit (4950 cycles) is passed on to detector D1 where it is heterodyned to the beat note of 100 cycles per 7 19,107 would be the frequency of cycles obtained by after as the bearingindicator, is connected in the output circuit of D1 by means of a selector switch, the connections of which are shown in Fig. 4. This bearing indicator shown'in Figs. 6 and 7 and described in detail later, is so constructed that when supplied with asource of power ofzero frequency, its two pointers will lie along the zero line pointing to bow, As the frequency is increased the pointers will rotate downwardly,

one in a clockwise, the other in a counter-duck wise direction. When supplied with 50 cycles they will assume a position indicating degrees and when the frequency is increased to 100 cycles they will be pointing at 180 degrees or at stern". This calibration holds only when the groundspeed of the ship is 30 knots per hour and when the sound source is 5000 cycles.

In the instrument shown in Fig. '7, the two pointers are similar in every way except they rotate in opposite directions, each having its in-,

dependent frequency meter movement and are connected electrically in parallel. The reason for providing two pointers is that there is an ambiguity when taking a bearing as to whether the fixed station is on the right or the left of the ship.

This fact makes it necessary for the navigator ---when in doubt as to which side of the ship the microphone station is located, to swing his ship while noting the reading of the bearing indicator. If the fixed station be ahead and on the right, swinging his ship to the right will, of course, bring both pointers nearer to the position marked tuned. The indicator is mounted upon a pedestel 300 which contains the entire mechanism.

The two moving elements 301, 302 of the bearing indicator are parts of the well known frequency indicating instrument known as a resonant frequencymeter. Two shafts 304, 305, mov-' ing the two pointers 306, 307 are concentric, the outer shaft being hollow so that the inner shaft turns within it. The pointers play over a graduated dial 303. This. bearing indicator usually gives only approximate bearings since to obtain a correct hearing it is necessary for the navigator to know the speed of the ship relative to the ground, which can,only be calculated roughly. The frequency of the sound wave must, of course, be correctly adjusted as must also that of the receiving heterodyne oscillator. A switch 308 is mounted in the base of the panel for disconnecting the indicator.

A more detailed description of the zero beat method such as would be practiced from the principles of this invention will now be given.

In an installation arrangement for the case of av zero beat method as shown in Figs. 9 and 10, assume for instance, a transmission system on shore, with arrangementsubstantially as in Fig.

.2. Let the carrier wavelength be 100 meters,

the intermediate frequencies be 15,000, 20,000

and 25,000 cycles respectively. Then the essential-radiations are comprised in a spectral band from 2974 to 3026 kilocycles. and these can be effectively handled by comparatively simple apparatus. The alteration of the 1,000 cycle note due to the Doppler effect is very closely a third of a cyclelper second for every knot speed in the direction of the receiving microphone, and with the receivingv equipment shown, is sumciently great to determine speeds correct-to the nearest knot.

The ship's installationwould be as shown in ing condenser 310 and regeneration control 311 for actuating the sound producer 319. Means of. the radio receiver, gang switch- 312, and beat regulator 313. Distances are recorded by recorder 314, and speeds directly indicated by tachometer 315 when the beat regulator has been adiusted to give zero beat at 1,000 cycles as indicated audibly by headphones 316.

Below decks is the motor-generator set 317, 318,

are provided in relays 320 and 321 for remote controlof the motor-generator set, and closure of the soundoscillator circuit. Field rheostats 322 and 323 are for adjusting the frequency and voltage of current supplied to the oscillator. The present beat arrangement does not require these to be constant, and in fact, the frequency might drift by as much as 20 cycles per second during the observations without afiectingthe accuracy oi the speed determination. For the insertion of a beating note into the receiver system, cor-re spending to vacuum tube oscillator 158 of Fig. 4, frequency changer 324 is used. This comprises a set of field coils, with phase splitting means in a well known manner for producing a rotating magnetic field, with speed of rotation equal to the electrical frequency of current produced by generator 318. These field windings are excited upon closure of relay 325. The armature of the frequency changer is rotated by means of motor 326, with reducing gear 327 interposed-between the motor armature and the armature of frequency changer 324. These armatures may be rotated in eith'er direction, under the control of the beat regulator 313. Connections are such that during operation, the line voltage is across the field wind ing of the motor-326, and also across the resistance of the regulator 313. The armature of the motor is connected between the mid tap of the field winding and the moving tap of the regulator. Consequently when the moving tap is set at the mid point of the regulator, there is no voltage across the armature winding and consequently no motion. If the pointer is displaced, however, armature current will be established, producing rotation in one direction if the pointer is moved to the right, and in the other if moved to the left. Further, the speed developed increases with the amount of the displacement.

The frequency of the current produced by frequency changer 324 will be the impressed frequency which isequal to that actuating the sound producer 319, increased by the speed of rotation. This resultant frequency is used to match the returning frequency and the Doppler effect is directly measured by the speed of rotation. The dial of the tachometer is calibrated in knots, and with a 1,000 cycle'tone indicates 30 knots when the Doppler effect of ten cycles per second change is' being matched ten revolutions of the fre quency changer per second, a

The operation of the equipment requires consecutive movement of the gang switch from the ofl" position through the different positions in succession. Turning toposition start switch 1) starts the motor-generator set, switch ,0 starts the motor which drives the distance recorder, switch d turns on filaments of the receiving set, and switch 2 connects the grid circuit of the audio amplifier tubes 331, 332, 333 to the negative of the A battery, for normal amplifying operation. Turning to position location which should be by a quick throw mechanism, switch a 5 operates keying relay 321 to cause the sound sig coming signals will cause an increase of the di- 96 justed that there is no current through the arms-- nals to be sent out from sound producer 319. At

the same time switch e places additional bias on the amplifier tubes, thereby cutting down on the current from the 3" battery through the recorder elements 334, 335, 336, to the plate ,of the amplifier tubes 337, 338 and 339 respectively.

This change of current causes displacement lines 340, 341, 342 on the recorder sheet, at the instant of sending out sound. After the sound has reached the microphones, radio signals-on the three intermediate channels will return to theradio receiver, and as above described will be separated out, signals from microphone 1 actuating only the amplifier tube 331, from microphone 2 actuating only amplifier tube 332,. and from microphone 3 actuating only the amplifier tube 333. I

since the bias on-these tubes is further nega-- tive than for undistorted amplificatiom the inrect current in the plate circuit, causing again displacements 343, 344, 345 on the recorder lines. The time intervals between the two sets of ofisets is equal to the time required for the sound to reach the successive microphones, since the other time intervals in the transmission and reception are negligible. 3

If the charts for the use of the navigator are to a scale of'1,000 yards per inch, it would be convenient to have the motor so driven that the recorder 1 tape will travel one inch in the time taken for sound to travel 1,000 yards. that is 0.6 second.

In this case, the distance between the offsets indicates directly the dstance to themicrophones in precisely the same scale as is used in the chart.

Having thus obtained data for plotting location, the operator will then turn the gang switch to determine speeds in the direction of microphones 1, 2 and 3 in turn. In each of thesepositions, switches a and b are operative, with sound going out from producer-3l9, switch c has stopped the recorder motor,.and turned on power to the beat regulator motor 326, and also has closed relay 325 to the field of the speed changer 324, switch d continues the receiving set in operation, while. switch c has again put the normal bias on amplifier tubes 337, 338, 339 for best amplification. For speed 1, the head phones 316are across the recorder element for tube 337, and therefore receives the eifect from microphone 1 only. For the other speed determinations the head phones are switched to tubes 338 and 339 inturn. Assumethe switch set for determination' of speed in the direction of microphone No. 1, and that the beat regulator motor 326 is at rest, due to the beat regulator resistance 313 being so adture of the motor. Suppose the current to the sound producer is,978 cycles per second, and the speed in the direction of microphone l is 15 knots, then due to the Doppler effect, the signal impressed on amplifier due to detected current from tube 328 will be of frequency 9'78 plus 5, or 983 cycles per second, since 15 knots produces a Doppler effect of 5 'cycles per-second when the original source is about 1,000 cycles. But the rotor of frequency changer 324'being at rest, there will be induced in it current of 9'78 cycles. -Con-' nections are such that the rotor feeds current into the plate circuit of detectors 328, 329, 330. Thus .both the 983 cycle current and the 9'78 cycle current are impressed on the amplifier tubeand actuate the headphones 316, causing the well known. beating effect, at'5 beats per second. This beat frequency is reduced to zero by rotating the armature of the frequency changer at 5 cycles per second opposite to the direction of the rotation of the magnetic field, thereby producing a frequency of-983 cycles which matches the 983 cycles per second due to the detected current. This matching is accomplished by turning the beat regulator and when accomplished; the speed in the reading on the chart, as for example drawn to scale of 1,000 yards represented by one inch.

The location at the time of making the tape record is found by striking of! from microphones 1, 2 and 3 in turn, arcs of radii r1, r2, 13 equal to.

the distances between ofisets on the tape. These three arcs intersect at the point P, which is the position at 4:15.

To determine the location after 5 minutes, for

example, a scale is provided showing distance travelled at difierent speeds. Suppose the'data is as shown that the speeds are '4, l0 and 3 knots toward microphones l, 2 and 3 respectively. Then these three values are sealed off from point P in the three directions, giving points S1, S2, S3. To find the resultant velocity of which these three values are components, lines are drawnthrough S1, S2 and S3, perpendicular to thelines PS1, PS2, PS3 respectively, and the point of intersection P will be the location to be expected after a flve minute interval, unless the course is changed. The distance PP may be scaled to determine the knots at which the ship is traveling,

As previously mentioned, the number of microphone stations and the corresponding number of modulating frequencies in the complex carrier wave may be considerably multiplied. Y

By the use of the invention described, several vessels may obtain bearings simultaneously on the same course, each ship using a distinctive frequency coupled with a distinctive call signal.

I claim:

1. The method of determining the'velocity and position of a ship at sea relative to a known point which comprises, generating and transmitting sound oscillations 'across the space intervening between a ship and a known point, receiving said sound oscillations, generating electroradiant oscillations, modulating said electroradiant oscillations by said received sound oscillations, transmitting said modulated oscillations across the space intervening between the known point and the ship, receiving said modulated oscillations and comparing the audio frequency component of the received oscillations with the sound oscillations originally transmitted to determine the relative motion of said ship with respect to said known point.

2. The method of determining the velocity and position oi a ship at sea relative to a plurality of known points which comprises, generating and transmitting sound oscillations across the space intervening between a ship and a plurality of known points, receiving said sound oscillations,

generating electroradiant oscillations in the form of a complex wave composed of high frequency oscillations modulated by a plurality of lower supersonlc frequency components, modulating each of said supersonic frequency components by the sound oscillations as received at each of said known points, transmitting said modulated oscillations across the space intervening between one of said known points and the ship, receiving said 3. A system for determining the location and .movement of a ship comprising, a sound wave oscillator having a predetermined frequency of oscillation, sound receiver stations for receiving sound waves produced by said sound wave oscillater, a wireless transmitting station associated with said sound receiver stations .for transmitting waves modulated in accordance with said received sound waves, a wireless receiving station for receiving said last mentione d'waves, said sound wave oscillator and wireless receiving station as one group and said sound receiver stations and wireless transmitter as a second group being variably disposed relative to .one another in distance and direction, and recording means associated with said wireless receiving station for recording the modulation frequency characteristicsof the waves received by the last mentioned' receiving means. I

4. A system for determiningthe location and movement of a ship comprising, a sound wave 05- cillator having a. predetermined frequency of oscillations, sound receiver stations for receiving the sound waves generated by said oscillator, a wireless transmitting station associated with said sound receiver stations for. transmitting waves modulated in accordance with said sound waves, a wireless receiving station for receiving said last mentioned waves, said sound wave oscillator and said wireless receiving station as one group and said sound receiver stations and wireless transmitter as a second group being variably disposed relative toeach other as regards distance and direction, and recording means including a graphic indicator for recording andindicatingthe intensity and modulation frequen'cy characteristics of the waves received by the wireless receivin station. I r

5. A system for determining the position and movement of a ship comprising, a local sound wave oscillator for producing and transmitting sound waves having a predetermined requency of oscillation, a radio transmitting station, a plurality of sound receivingstations connected electrically to said radio transmitting station, said radio station being adapted to transmit complex waves modulated by said sound waves as received by each of said sound receiver stations, a receiving station for receiving the complex 'modulated waves, said sound wave oscillator and said.

wireless receiving station .as one group and said sound receiver stations and wireless transmitter as a second group being variablydisposed relative to one another as regards distance and ditransmitting station, sound receiver stations located at a distance from the ship and from each other and conductively connected to said radio transmitting station, means at'said radio station for transmitting complex waves modulated by said sound waves, each component of the complex wave beingmodulated by one of the sound receivers, a local receiving station for receiving said complex modulated waves and recording and indicatingmeans for graphically and continually indicating the modulation frequency characteristics of the received complex wave, said indicating means being calibrated to indicate the direction of the movement as well asthe amount of the motion. a

l. A method for determining the position and movement of a ship which consistsin transmitting sound waveshaving a predetermined frequency of oscillation from the ship, generating a complex electric wave, receiving said sound waves at known points, and modulating said complex electric wave thereby, transmitting the .modulated'complex electric wave, receiving said electric waves upon the ship and comparing the 5 relative intensities andfrequencies of the sound frequency components of the said complex wave,

and the original sound wave frequency.

8. A method of determining the velocity of a ship at sea relative to known points which consists in transmitting sound waves having a predetermined frequency of oscillation, receiving the sound waves atvarlous known points, generating a complex electric wave,- modulating said complex electric wave by the received sound waves, transmitting the modulated complex electric wave receiving said electric waves, heterodyning each component oi the received-electric .wave to I produce a beat notefrom each component, recording the beat note of each component wave and measuring the recorded beat note to indicate the ships velocity relative to said known points.

9. A method for determining the position of a ship which consists in transmitting spund waves from the ship, receiving said sound waves at known points upon land, generating a complex electric carrier wave, causing these received sound waves to modulate the intermediate frequency components of said complex electric carrier wave,

radiating said carrier wave into space, receiving the modulated electric wave upon the ship, detecting, said electric wave to produce the intermediate frequency components thereof, again detecting to produce the sound frequency components of said intermediate frequency components and graphically recording the amplitude of the current values of each intermediate frequency component of the radiated carrier wa've relative to the speed of the ships propeller to determine the position of the ship. r 10. The method for determining the ground speed of a ship which consists in transmitting sound waves having a predetermined frequency of oscillation from the ship, receiving said sound waves at known points on the land, generating a complex electric carrier'wave, modulating the intermediate frequency components of said complex electric carrier wave by said received sound 'ing said electric wave to reproduce intermediate frequency components thereof, heterodyning each intermediate frequency component of the electric wave by theorlginally transmitted soundfrequency, recording each resulting beat note, and

the record produced thereby to indis cate the velocity of the ship relative to each of said-known points.

11. A systemfor determining the location and ceiving said last mentioned waves, said sound wave oscillator and wireless receiving station as one groupand said sound receiver stations and 1 wireless transmitter as a "second group being variably disposed relative to one another, in distance and direction, andrecording means associated with said wireless receiving station for recording the intensity of the modulation frequencies of the waves received by the lastmentioned receiving means. a t

12. A system for determining the'location and movement of a ship comprising, a sound wave oscillator having a predetermined frequency of oscillation, sound receiver stations for receiving sound waves produced by said sound wave oscillator, a wireless transmitting station associated with said sound receiver stations for iransmitting waves modulated accordance with said received sound waves, a. wireless receiving station for receiving said last mentioned waves, said sound wave oscillator and wireless receiving station as one group and said sound receiver stations and wireless transmitter as a second group being variably disposed relative to one another in distance and direction, and indicating means associated withsaid wireless receiving station for indicatingthe modulation frequency characteristics of the waves received by the last mentioned receiving means.

13. A systemffor determining the location and movement. of a ship comprising, a sound wave oscillator having a predetermined frequency of oscillation, sound receiver'- stations for receiving sound waves produced by said sound wave oscillator, a wireless transmitting station associated with said sound receiver stations for transmitting waves modulated in accordance with said received sound waves, a wireless receiving station for receiving said last mentioned waves, said sound wave. oscillator and wireless receivingstation as one group and said sound receiver stations and wireless transmitter as a second group being variably disposed relative to one another in distance and direction, and indicating means associated with said wireless receiving station for" indicating the frequency and intensity of the modulation frequencies of the waves received by the last mentioned receiving means.

14. A method for determining the position of a ship which consists in transmitting sound waves from the ship, receiving said sound waves at known points upon land,. generating a complex electric carrier wave, causing these received sound waves to modulate the intermediate 'frequency components of said complex electric carrier wave, radiating said carrier wave into space, receiving the modulated electric wave upon the ship, de-

tecting said electric wavetoproduce'the intermediate frequency components thereof, again detecting to produce the sound frequency com ponents of said intermediate frequency components and observing the amplitude'of the current values of each intermediate frequency com-' ponent of the radiated carrier waverelative to v the speed of the ship's propeller to determine the position of the ship.

15. A system for determining the location and movement of a ship comprising, a Sound wave oscillator having a predetermined frequency of oscillation, sound receiver stations for receiving the sound waves generated by said oscillator, a wireless-transmitting station associated with said sound receiver stations for-transmittingwaves modulated in accordance with said sound waves, a wireless receiving station for receiving said last mentioned waves, said sound wave oscillator and 'said wireless receiving station as one group and said sound receiver stations and wireless transmitter as a second group being variably disposed relative to each other as regards distance and direction, and recording means for recording the intensity and modulation frequency characteristics of'the waves received by the last mentioned receiving means. j

16. A system for determining the position and movement of a ship comprising, a local sound wave oscillator having-a predetermined frequency of bscillation for producing and transmitting sound waves, a radio transmitting station, a plurality of sound receiving stations connected electrically to saidradio transmitting station said radio station being adapted to transmit complex waves modulated by said sound waves as received by each of said sound receiver stations, a receive ing'station for receiving thecomplex modulated waves, said sound wave oscillator and said wireless receiving station as one group and said sound receiver stations and wireless transmitter as a.

second group being variably disposed relative to one anotheras regards distance and direction, and indicating means for graphically and continuously indicating the intensity and audio frequency characteristics of the component partsof the received'radio wave.

17. A method for determining the position and- V movement of a ship which consists, in transmittingsound waves having a, predetermined frequency from the ship, generating a complex electric wave, receiving said'soun'd'waves atknown 'points, and modulating said complex electric wave thereby, transmitting the modulated-com .plex electric wave; receiving saidelectric waves upon-the-ship and recording the relative intcnsi- I60.

tiesand frequencies of the sound frequency components'of the said complex wave, and the original sound wave frequency.

' Q 18.;A method for determming the position and movement of a ship which consists in transmitting sound waves having a predetermined frequency from the, ship, generating a complex electric wave, receiving said sound waves at known points,

' and modulating said complex electric wave thereby, transmitting the modulated complex electric wave, receiving said electric waves' upon the ship and recording and observing the relative intensities and frequenciesof the sound frequency componentsof the said. complex wave; and the orig inal sound wave frequency.

19. A system for determining the position and movement of a ship comprising, a local. sound wave oscillator having a predetermined frequency of oscillation forproducing and transmitting sound waves, a radio transmitting station, aplurality of sound receiving stations connected electrically' to said radio transmitting station, said radio station beingv a apted to transmit complex .waves modulated by saidsound waves as received Y by each of said sound receiver stations, a receiving station for receiving the complex modulated waves, said sound wave oscillator and said wireless receiving station as one group and said sound receiver stations and wireless transmitter as a second group being variably disposed relative to one another as regards distance and direction, and recording and indicating means for graphically and continuouslyrecording the frequency and intensity of the component parts of the received radio wave.

graphically indicating and recording the amplitude of the current values of each intermediate frequency component, of the radiated carrier wave relative to the speed of the ships propeller to determine the position of the ship.

21.- A method for determining the velocity of a ship at sea relative to known points which consists in transmitting sound waves, having a predetermined frequency, receiving the sound waves at various known points, generating a complex electric wave, modulating said complex electric wave by the 'eceived sound waves, transmitting the modulated complex electric wave; receiving said electric waves, heterodyningeach component of the received electric wave to produce a beat note from each component, recording and indicating the beat note of each component wave and measuring the recorded beat note to indiv'elocity. relative to said knowncate the ship's points.

22. Themethod for determining the speed of' a ship relative to a fixed point which includes the step of transmitting an audio frequency signal by a slow transmitting medium between the two, receiving and retransmitting the signal in the reverse direction between the two through an instantaneous transmittingmedium, receiving the retransmitted signal at the transmitting stationand comparing the frequencies of the transmitted signal and the' signal finally received thereat.

23.- The method of determining the velocity and position of a moving object relative. toa pluraliiy of known points which comprises, generating and transmitting sound oscillations across the space intervening between the object and a: plurality of known points, receiving said sound oscillations at each of said known points, generating n electro-radiant oscillations in the form of a complex wave composed of high frequency oscillations modulated by a plurality of -lower supersonic frequency components, modulating eachof said supersonic frequency compo-- nents by the sound oscillations as received at each of said knownpoints, transmitting said modulated oscillations across the space intervenin'g between one of said known points and the object, receiving said-modulated oscillations and. comparing the various sound frequency compo-' .nents thereof with each other and with'the sound oscillations originally transmitted to de-. termine the position and relative motion of the object with respect to said known points.

- for receiving said last mentioned waves said sound wave oscillator and wireless receiving station as one group and said sound receiver stations and wireless transmitter as a second group being variably disposed relative to one another 16 in distance and direction, and means associated with said receiving station for determining the modulated characteristics of the received waves for determining ,the location and movement of the ship.

{25. A system for obtaining a ship's location and movement comprising a sound wave oscillator, microphone stations for receiving sound waves, a wireless transmitting station associated lated energy at the object, demodulating the received energy so as to derive therefrom the various energy wave components, determining,

the positicnof the object with respect to said known points by noting the relative intensity of the various energy wave components receivedat said points as derivedfrom the intercepted transmitted modulated energy and determining the velocity and direction of movement of the object by noting the relative frequency characteristics.

of the various energy wave components received at said points as derived from the intercepted with each of said microphone stations for trans-1' transmitted d a d e gy.

mitting waves modulated in. accordance with said tervening between the known points and the object, receiving said modulated oscillations, deriving therefrom the various sound oscillations and comparing the intensity of said various derived sound oscillations. f s 2'7. The steps in a method of velocity deter- Amination of an object which comprise determining the velocitlyof the object in a plurality of directions by generating and transmitting sound oscillations across the space intervening between the object and several known points, receivingsaid sound'oscillations at said points, generating electroradiant oscillations, -modulating said electro-radiant oscillations f by said received sound oscillations, transmitting said modulated oscillations, receiving said modulated oscillations at the object and deriving therefrom the varioussound oscillations arid-comparing the frequency of the various derived sound oscillations with the frequency of the sound oscillations as originally generated at the object. r

- 28. The steps in a method of charting the course and-predicting the future position of a moving object. which comprise, generating and transmitting energy waves of .a predetermined ogi frequency across the space intervening between the object and several known points, receiving said energy waves at said points; generating electroradiant oscillations, modulating said electroradiant oscillations by said receivedeenergy waves, transmitting said modulated oscillations,

receiving said modulated oscillations atthe ob i'c't and derlvins therefrom the various energy waves, comparing the intensity of said various derived energy waves and comparing the .fre' quency of the various derived energywaves.

future position of a moving object relative to known points which comprise,"transmitting energy waves from the objecthaving a predeter- 30. The steps in a method of predicting the mined frequency ofoscillatlon, receiving the energy wavesat various known points, generating carrier frequency energy, modulating the carrier frequency energy with. the energy waves as re- 'ceived from at least two of said points, transmitting the resultaint modulated energy, intercepting the transmitted modulated energy at the object,

demodulating the intercepted energy so as to derive therefrom and identify the various energy wave components as received at each of said varioiis known points, determining the position of the object with respect to said known points by noting certain of the characteristics of the various energy wave components as derived from the transmitted modulated energy and determiningthe velocity and direction of movement of the object by noting certain other characteristics of the energy wave components as derived from the transmitted modulated energy.

31. A method of predicting the future position of a moving object relative to known points which includes the steps of transmitting from the object, low frequency waves of a predetermined frequency, receiving the low frequency waves at various known points, generating a complex electric wave, modulating the compler': electric wave by the received low frequency waves, transmitting the resultant modulated energy, receiving the transmitted energy at theobiect and deriving from the received energy the low frequency modulation components, determining the position of the object with respect to the said points by noting the relative intensity of the derived low frequency modulation I components, generating a heterodyne frequency; beating each of the low "frequency wave componentsjwith the generated heterodyne frequency and producing therefrom a resultant beat note foreaeh of said components and determining the ship's velocity and direction of movement thereof relative to said known points by noting the relative frequency of each 'lmown points which comprise transmitting low frequency waves from the object to a plurality of known points, receiving the transmitted low frequency waves at the said known points. selectively modulating electro-radiant energy with the received lowfrequency waves, transmitting the modulated eleetro-radiant energy, receiving the transmitted energyand determining the position of the object, the-velocity thereof and its direction ofmovement by comparing. the intensities of the various low frequency components of the received energy and comparing the frequency of each of the low frequency components of'the received energy with a standard frequency.

, 33, A method of predicting the future position of a moving object relative to a knownpoint 'Q which includes thev steps of transmitting from the object energy waves of a known frequency,

receiving the transmitted en'ergy waves as vii-1m known points, generating electro-radiant energy :and selectively modulating the generated electroradiant energy by the energy waves received at said points, transmitting the resultant modulated energy, receiving the transmitted energy and deriving therefrom each of the modulation'components, determining the position of the object with respect to said point by noting the relative intensity of the derived modulation components, determining the direction of mov ment and the velocity of the object with respec to said point by noting the degree of chime in frequency and the direction or the change from a mean value.

norm; HAYS mom, on. 

